1,428 research outputs found
Cooperative Precoding with Limited Feedback for MIMO Interference Channels
Multi-antenna precoding effectively mitigates the interference in wireless
networks. However, the resultant performance gains can be significantly
compromised in practice if the precoder design fails to account for the
inaccuracy in the channel state information (CSI) feedback. This paper
addresses this issue by considering finite-rate CSI feedback from receivers to
their interfering transmitters in the two-user multiple-input-multiple-output
(MIMO) interference channel, called cooperative feedback, and proposing a
systematic method for designing transceivers comprising linear precoders and
equalizers. Specifically, each precoder/equalizer is decomposed into inner and
outer components for nulling the cross-link interference and achieving array
gain, respectively. The inner precoders/equalizers are further optimized to
suppress the residual interference resulting from finite-rate cooperative
feedback. Further- more, the residual interference is regulated by additional
scalar cooperative feedback signals that are designed to control transmission
power using different criteria including fixed interference margin and maximum
sum throughput. Finally, the required number of cooperative precoder feedback
bits is derived for limiting the throughput loss due to precoder quantization.Comment: 23 pages; 5 figures; this work was presented in part at Asilomar 2011
and will appear in IEEE Trans. on Wireless Com
Delivery Time Minimization in Edge Caching: Synergistic Benefits of Subspace Alignment and Zero Forcing
An emerging trend of next generation communication systems is to provide
network edges with additional capabilities such as additional storage resources
in the form of caches to reduce file delivery latency. To investigate this
aspect, we study the fundamental limits of a cache-aided wireless network
consisting of one central base station, transceivers and receivers from
a latency-centric perspective. We use the normalized delivery time (NDT) to
capture the per-bit latency for the worst-case file request pattern at high
signal-to-noise ratios (SNR), normalized with respect to a reference
interference-free system with unlimited transceiver cache capabilities. For
various special cases with and that satisfy , we establish the optimal tradeoff between cache storage and latency. This
is facilitated through establishing a novel converse (for arbitrary and
) and an achievability scheme on the NDT. Our achievability scheme is a
synergistic combination of multicasting, zero-forcing beamforming and
interference alignment.Comment: submitted to ICC 2018; fixed some typo
Cellular Underwater Wireless Optical CDMA Network: Potentials and Challenges
Underwater wireless optical communications is an emerging solution to the
expanding demand for broadband links in oceans and seas. In this paper, a
cellular underwater wireless optical code division multiple-access (UW-OCDMA)
network is proposed to provide broadband links for commercial and military
applications. The optical orthogonal codes (OOC) are employed as signature
codes of underwater mobile users. Fundamental key aspects of the network such
as its backhaul architecture, its potential applications and its design
challenges are presented. In particular, the proposed network is used as
infrastructure of centralized, decentralized and relay-assisted underwater
sensor networks for high-speed real-time monitoring. Furthermore, a promising
underwater localization and positioning scheme based on this cellular network
is presented. Finally, probable design challenges such as cell edge coverage,
blockage avoidance, power control and increasing the network capacity are
addressed.Comment: 11 pages, 10 figure
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